The present invention relates to a temperature sensing device for test cylinder, and more particularly to a temperature sensing device having a sensing element being directly located at a position best for accurately sensing the temperature of the test cylinder.
Please refer to FIG. 1 in which a conventional temperature sensing bar 9 is shown. The temperature sensing bar 9 includes a length of straight hollow cylindrical casing 90 put around an outer periphery of an end of a multi-conductor cable 91, and a resistance-type thermal-sensitive sensing element 2 suspended in the casing 90 and connected to two conductors 911 of the cable 91. Epoxy resin is injected into the casing 90 to locate the originally suspended sensing element 2 so that it is not easily shifted in the casing 90. A temperature sensed by the temperature sensing bar 9 is sent by the cable 91 to a remote receiving end and be received thereat for logic operation. The following are three major problems with the conventional temperature sensing bar 9 that have not been effectively solved up to date:
1. When the temperature sensing bar 9 alone is used to sense a temperature, it would be difficult for the bar 9 to sense the temperature of a test cylinder 6, because both the bar 9 and the test cylinder 6 are round members and there is not a contact surface between them large enough for the bar 9 to accurately sense the temperature of other areas of the test cylinder 6 that do not contact with the bar 9.
2. The epoxy resin injected into the casing 90 to locate the sensing element 2 has a resistance larger than that of water and therefore results in the problem of failing to locate the sensing element 2 in the casing 90 at an ideal position due to the resistance and buoyancy of the epoxy resin. When the sensing element 2 is located in the casing 90 at a position too close to the cable 91, a distance from the close end of the casing 90 (i.e. the right end of the casing 90 in FIG. 1) to the sensing element 2 exceeds a predetermined valve that results in an increased impedance and accordingly a less sensitive transmission of heat and delayed heat transmission at the closed end of the casing 90. Moreover, when the resistance of the epoxy resin causes the sensing element 2 to deviate from an acceptable position to contact with an inner surface of the casing 90, the sensing element 2 shall have a largely reduced temperature sensing ability and thermal sensitivity.
3. The cable 91 connected to the temperature sensing bar 9 is frictionally fitted in the casing 90. When the bar 9 is used to sense temperature and therefore repeatedly subject to thermal expansion and contraction for a long term, there would be play occurred at joints of the casing 90 and the cable 91. Such play would cause the problem of poor waterproof to admit liquid into the casing 90 via the play and therefore wets and causes failure of the sensing element 2. Although the epoxy resin is adapted to bond the cable 91 and the casing 90 at their joint, the frequent thermal expansion and contraction of the bar 9 would still destruct the bond between the cable 91 and the casing 90 and eventually produce play between the two members to admit liquid into the casing 90.
To overcome the first one of the above-mentioned drawbacks existing in the conventional temperature sensing bar 9, a conventional temperature sensing structure shown in FIG. 1 and currently prevail in the market is developed. Such structure mainly includes a binding belt 85, a heat-transfer member 7, a seat 8, and a temperature sensing bar 9 as previously described. The seat 8 is provided at one end with an opening 80, at the other end with open-topped first and second recesses 81 and 82 that are axially communicable with each other, and at two longitudinal sides with two integrally and symmetrically formed side projections 83 that have vertical through holes 831 provided therein. The heat-transfer member 7 is in the form of a cubic block having a concave top surface 70 and an axially extended insertion hole 71 below the top surface 70. The binding belt 85 has an end formed of a through hole 851.
As can be seen from FIGS. 2 and 3, when the heat-transfer member 7 is set in the first recess 81(not shown)on the seat 8 and the temperature sensing bar 9 is upward extended through the opening 80 (not shown) at one end of the seat 8 into the second recess 82 and inserted into the insertion hole 71(not shown)on the heat-transfer member 7, the temperature sensing structure is ready for use. By positioning the test cylinder 6 on a top of the seat 8, a bottom of the test cylinder 6 will fitly and closely contact with the concave top surface 70 of the heat-transfer member 7. To bind the test cylinder 6 to the seat 8, the binding belt 85 is located above the test cylinder 6 with two ends thereof downward extended through the two through holes 831 on the two side projections 83 of the seat 8. Thereafter, one end of the binding belt 85 is extended through the hole 851 provided on the other end of the binding belt 85 to tighten the bind belt 85 around the test cylinder 6 and the seat 8.
A problem with the above-described temperature sensing structure is the test cylinder 6 is subject to repeated thermal expansion and contraction and would finally cause fatigue of the binding belt 85 that normally contacts with it, and the fatigued binding belt 85 would fail to tightly bind the test cylinder 6 and the heat-transfer member 7 together to result in inaccurate sensing of temperature. A common example of such situation is an air conditioner having temperature-control or thermostatic-control ability. If a temperature sensing structure in the air conditioner fails to accurately and correctly sense a room temperature, the room temperature regulated by the air conditioner would be either too high or too low. It is therefore very important to always keep the test cylinder and the heat-transfer member of the temperature sensing structure tightly contacting with each other.
Since the currently prevail temperature sensing structure still employs the conventional temperature sensing bar 9 in sensing the temperature of the test cylinder 6, the second and the third drawbacks as previously described still exist and could not be effectively overcome. That is, the sensing element 2 could not be accurately located in the temperature sensing bar 9 and it is possible liquid would permeate into the temperature sensing bar 9 to damage the latter.
A primary object of the present invention is to provide a temperature sensing device for test cylinder that includes a sensing element that could be directly accurately located at a desired position best for correctly sensing a temperature of the test cylinder, and a structure that allows automatic draining of any liquid permeated into the device for the device to always function well.
Another object of the present invention is to provide a temperature sensing device for test cylinder that includes a heat-transfer member having a concave top surface that is the only surface closely and fitly contacting with the test cylinder for temperature sensing purpose and therefore enables accurate sensing of temperature of the test cylinder. A further object of the present invention is to provide a temperature sensing device for test cylinder that includes a temperature sensing unit and an elastic fixing unit, so that the temperature sensing unit and the test cylinder are entirely and perfectly received in the fixing unit to be always firmly bound together by the fixing unit.
A still further object of the present invention is to provide a temperature sensing device for test cylinder that includes a heat-transfer member having multiple channels provided at a bottom side for accommodating multiple conductors therein, so that a signal representing the temperature sensed by the sensing element can be sent to and received at multiple remote receiving ends.